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The setup is the same as an AOV except we use a light path expression instead of an AOV channel name. We can also use a short descriptive name (e.g. lpe:diffuse) as well as the long LPE expression (e.g. lpe:CD<L.>CD[<L.>O]).

Additionally, we can group the outputs by light groups and/or by geometry set up by a lpegroup.


For DisplayChannel, we can use either the short name or long expression, e.g., lpe:diffuse or lpe:CD<L.>CD[<L.>O]

Code Block
DisplayChannel "color lpe:diffuse"


Code Block
DisplayChannel "color lpe:CD<L.>CD[<L.>O]"

Basic LPEs

For basic workflows, the following LPE are recommended. Note that we are specifying the DisplayChannel and a name (which can be most anything). Note that these LPE will collect the light interaction from different lobes of materials and store them in the same AOV. For example: reflections from the Glass Lobe in PxrSurface will be combined with other specular reflections in the direct and indirectSpecular AOVs. This can simplify the outputs.


Note that the first eight of these expressions are both disjoint and exhaustive; any individual light path will match exactly one of them. As a result, rendering out all eight of them and then compositing them together will produce the equivalent of the beauty image.


Caustics are not included in the built-in list because they overlap with lpe:indirectdiffuse. with indirectdiffuse lpe:C<RD>[DS]+[<L.>O] However, you can select caustics with the expression lpe:CD[S]+[<L.>>O]

Custom LPE

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